Hardware overvoltage disconnecting circuit

This application is a U.S. National Stage Application of International application No. PCT/CN2007/000508. filed Apr. 13, 2007 which was published in English as WO 2007/118400 on Oct. 25, 2007. This application claims the benefit of Chinese Application No. 200610074786.7, filed Apr. 13, 2006. The disclosures of the above applications are incorporated herein by reference.

The present invention relates to a field of voltage detection and control, and particularly relates to a hardware overvoltage disconnecting circuit which disconnects the power supply module (rectifier module) from the power network when the AC power network is in the state of overvoltage.

In the prior art, there is a blind area about overvoltage protection, that is, at the moment of power on, the module input overvoltage protection is performed by the protection circuit of the module in normal work state. In this way, there exists a problem of the delayed protection. Therefore, the power supply module may have a possibility of breaking down or may break down immediately. In addition, a second auxiliary power supply board is required to identify and determine the input voltage after the power supply module is disconnected, so as to re-connect the power supply module to the system after the voltage of the power network is lowered. However, this leads to increased costs and decreased reliability

The object of the present invention is to provide a hardware overvoltage disconnecting circuit which can response timely and implement immediate protection when the power supply module are power-on, so that the power supply module is disconnected from the power network when the voltage of the power network increases to a predetermined value (or when both the voltages of the power network and the DC busbar reach the predetermined value), and the power supply module is connected to the power network when the voltage of the power network comes back to a certain value (or when both the voltages of the power network and the DC busbar come back to the certain value).

In order to achieve the above-mentioned object, the present invention provides a hardware overvoltage disconnecting circuit that comprises a disconnecting relay and a voltage detection circuit. The disconnecting relay is connected in series between an AC power network and a power factor correction circuit of a power supply module. A first sampling terminal of the voltage detection circuit samples the voltage of the AC power network between the AC power network and the disconnecting relay, and an output of the voltage detection circuit is connected to a control terminal of the disconnecting relay. When the AC power network is in the state of overvoltage, the disconnecting relay is disconnected and the power supply module is disconnected from the AC power network. When the voltage of the AC power network is normal, the disconnecting relay is connected.

As an improved embodiment, the voltage detection circuit further comprises a second sampling terminal for sampling a voltage of a DC busbar in the DC busbar of the power supply module. When the AC power network and the DC busbar are both in the state of overvoltage, the disconnecting relay is disconnected, and the power supply module is disconnected from the AC power network. When the voltages of the AC power network and the DC busbar are both normal, the disconnecting relay is connected to the power supply module.

As a embodiment of the present invention, the disconnecting relay is connected in series between the AC power network and a rectifier filter circuit of the power supply module.

As another embodiment of the present invention, the circuit of the present invention comprises two disconnecting relays respectively connected in series between the AC power network and two inputs of the power factor correction circuit. Both the control terminals of the disconnecting relays are connected to the output of the voltage detection circuit.

Specifically, a switch of the disconnecting relay is connected to one terminal of the AC power network. A normally closed contact of the disconnecting relay is connected to one input of the rectifier filter circuit, and a normally opened contact is floating. A first terminal of a winding of the disconnecting relay is coupled to the DC power supply, and a second terminal of the winding as a control terminal is connected to the output of the voltage detection circuit

Further, the circuit of the present invention further comprises a current limiting resistor connected in series between the AC power network and the disconnecting relay.

When the circuit of the present invention only samples the voltage of the AC power network, the voltage detection circuit comprises a AC voltage detection section and a driving section that are connected in series. The AC voltage detection section comprises a voltage sampling unit and a peak-holding and logic-judging unit that are connected in series. An input of the voltage sampling unit is used as the sampling terminal of the voltage detection circuit, and an output of the driving section is used as the output of the voltage detection circuit.

When the circuit of the present invention samples the voltage of the power network and the DC busbar simultaneously, the voltage detection circuit comprises an AC voltage detection section, a busbar voltage detection section and a driving section. The AC voltage detection section comprises a voltage sampling unit and a peak-holding and logic-judging unit that are connected in series. An input of the voltage sampling unit and an input of the busbar voltage detection section are used, respectively, as the first sampling terminal and the second sampling terminal of the voltage detection circuit. The output of the peak-holding and logic-judging unit and the output of the busbar voltage detection section are coupled to each other, and a control signal is outputted to the driving section. An output of the driving section is used as the output of the voltage detection circuit.

Further, the voltage sampling unit mainly comprises a first diode, a second diode, a fifth resistor and a sixth resistor. An anode of the first diode is connected to one input of the AC power network. A cathode of the first diode is connected to a cathode of the second diode, and then is connected to one terminal of the fifth resistor. An anode of the second diode is connected to the other input of the AC power network. The other terminal of the fifth resistor is connected to one terminal of the sixth resistor. An output of the voltage sampling unit is coupled to an input of the peak-holding and logic-judging unit. The other terminal of the sixth resistor is grounded.

Further, the peak-holding and logic-judging unit mainly comprises a first operational amplifier and a first comparator. A noninverting input of the first operational amplifier is connected to an output of the voltage sampling unit, an inverting input of the first operational amplifier is connected to a noninverting input of the first comparator, and an output of the first operational amplifier is connected to the noninverting input of the first comparator by a series branch composed of a resistor and a diode, for holding the peak. An inverting input of the first comparator is coupled to a first reference source, the noninverting input of the first comparator is connected to its output by a series branch composed of a resistor and a diode, and the output of the first comparator is used as the output of the peak-holding and logic-judging unit. The inverting input of the first operational amplifier and the inverting input of the first comparator are both grounded by a resistance-capacitance parallel branch.

Further, the driving section is a switch transistor. The base of the switch transistor is used as an input of the driving section and is grounded by a resistor. The collector of the switch transistor is used as the output of the driving section, and is connected to the control terminal of the disconnecting relay. The emitter of the switch transistor is grounded.

Specifically, the busbar voltage detection section mainly comprises a second comparator. A noninverting input of the second comparator is used as a second input of the voltage detection circuit, and is connected to an output of the second comparator by a series branch composed of a resistor and a diode. An inverting input of the second comparator is coupled to a second reference source. An output of the second comparator is used as the output of the busbar voltage detection section.

The hardware overvoltage disconnecting circuit of the present invention samples the voltage value from the AC input of the power supply module, and disconnects the power supply module (typically the rectifier module in the power supply module) from the power network before the voltage of the power network reaches its extreme value, such that the protection circuit is started up before the busbar voltage reaches its extreme value, and the relay can still work even if only the auxiliary power supply is working among all the components of the power supply module. The circuit of the present invention simultaneously detects the DC busbar voltage, which functions as one of the factors used to determine whether or not the relay is to be disconnected. Thus a false protection resulted from a transient overvoltage is avoided. Meanwhile the circuit of the present invention continuously monitors the voltage of the power network (or simultaneously monitoring the voltage of the DC busbar) after the power supply module is disconnected from the power network, and re-connects the power supply module to the power network when the voltage of the power network returns to a certain value, thus the disconnecting relay 1 works in a hiccup mode. The circuit of the present invention always keeps the auxiliary power supply of the module in a work state by the intermittent charging of the busbar capacity. A peak holding circuit is used in the voltage detection circuit 2, such that the power supply module still has accurate sample value after the power supply module is disconnected from the AC power network. Meanwhile, the series connection of the disconnecting relay 1 and the current limiting resistor mitigates the startup current and restricts the charging voltage, and also functions to protect the relay and downsize the relay, and thus the cost of the system is reduced.